Engine starter gearing



May 17, 1955 BUXTQN 2,708,370

ENGINE STARTER GEARING Filed May 15, 1954 2 Sheets-Sheet l 33 36 5.9 a;a5 a? INVENTOR. WITNESS: James 673M521 BY M- 54642: W

A TOBNEY May 17, 1955 Filed lay 1a, 1954 J-E. BUXTON ENGINE STARTERGEARING 2 Sheets-Sheet 2 llllllll WITNESS mmvrox BY 4 m A OBNEY UnitedStates atent ENGINE STARTER GEARING James E. Buxton, Elmira, N. Y.,assignor to Bendix Avialion Corporation, a corporation of DelawareApplication Diary 13, 1954, Serial No. 429,533

8 Claims. (Ci. 747) The present invention relates to engine startergearing, and more particularly to a heavy duty type of drive whichmaintains its engagement with the engine until it is in satisfactoryoperation.

It is an object of the present invention to provide a novel heavy dutystarter drive of this type which is ch cient and reliable in operation,simple and economical in construction and small in overall dimensionsrelative to its torque capacity.

It is another object to provide such a device which is largelyself-contained and enclosed against access of foreign matter.

It is another object to provide such a device incorporating a frictioncoupling which is normally spring-loaded with light pressure, but whichis automatically compressed as the driving load is assumed.

Further objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation, partly broken away and in section of apreferred embodiment of the invention showing the parts in normal oridle position;

Fig. 2 is a similar view showing the parts in cranking position;

Fig. 3 is a similar view showing the parts in the positions assumedwhile the engine is running with the drive maintained in mesh;

Fig. 4 is a similar view showing the relationship of the parts in caseof tooth abutment between the pinion and engine gear during the meshingoperation; and

Fig. 5 is an enlarged detail of the spring structure controlling theoverrunning clutch.

In Fig. 1 of the drawing there is illustrated a power shaft 1 which maybe the extended armature shaft of the starting motor not illustrated. Adrive shaft 2 which is hollowed out for a portion of its length as shownat 3 is telescoped over the end of the power shaft and fixed thereon asby means of keys 4 and set screw 5. The drive shaft is reduced indiameter from a point adjacent its anchorage to the power shaft 1, thusforming a shoulder 6. This reduced section is threaded for a portion ofits length as indicated at 7, and a control nut 3 is mounted on saidthreaded portion for rotary and traversing movement. A pinion 9 isslidably journalled on the unthreaded portion of the drive shaft 2 formovement into and out of mesh with a gear 11 of the engine to bestarted, the meshing position of the pinion being defined by a stop nut12 fixedly mounted on the drive shaft.

Means for actuating the pinion 9 from the control nut 8 is providedcomprising a barrel member 13, and a pinrality of friction couplingdiscs 14 splined alternately to the control nut and barrel member andyieldingly pressed together by means of compression springs 15. For thispurpose, a pressure disc 16 is held in the barrel 13 by a lock ring 17,and a dished annular thrust member 13 is similarly positioned in thebarrel 13 by a lock ring 19; the springs 15 being located between thethrust plate 18 and a thrust plate 21 retained on the control nut 8 by alock ring 20.

In order to transmit the longitudinal movement of the control nut 8 tothe barrel 13 in the meshing direction, the thrust disc 16 is anchoredto the control nut by any suitable means such as a lock ring 22.

Means for actuating the pinion from the barrel 13 is provided in theform of driving clutch disc 23 splined in the barrel and provided withoverrunning clutch teeth 24 normally engaging similar teeth on a flange25 formed on the hub of the pinion. Means for normally holding theclutch teeth in engagement is provided comprising a thimble 26 retainedin the end of the barrel 13 by a lock ring 27 surrounding the flange 25of the pinion and having an inwardly directed flange 38. A plurality oflight compression springs 28 (Fig. 5) are mounted on studs 29, looselyretained in an annular channel member 31 seated against the flange 30.The heads 32 of the studs 29 bear against the flange 25 of the pinionand thus yieldingly press the pinion against the driving clutch disc 23.

A series of mesh-enforcing compression springs 33 are located betweenthe thrust plate 18 and the driving clutch disc 23 to normally maintainthe parts in extended relation, as shown in Fig. l. 7

Means are provided for latching the pinion 9 in mesh with the enginegear 11 until the pinion is rotated above a predetermined minimum speed.For this purpose a latch member 34 is mounted for radial slidingmovement in the flange 25 of the pinion, and is yieldingly pressedagainst the driving shaft 2 by means of a spring 35 retained by a cupmember 36 having a press fit in the pinion flange. The drive shaft isprovided with an annular recess 37 in position to receive the latchmember 34 when the pinion is meshed with the engine gear, and therebyprevent the demeshing movement of the pinion until the latch iswithdrawn by centrifugal. force.

in order to prevent the pinion from drifting away from its idleposition, a recess 38 is formed in the drive shaft in position toreceive the latch member 34 when the parts are in idle position, and therecess is formed with an inclined shoulder 39 which cooperates with thelatch to yieldingly resist such drifting movement of the pinion.

In operation, starting with the parts in the positions illustrated inFig. l, rotation of the power shaft 1 in the direction of the arrow istransmitted to the drive shaft 2,

and thus causes the control nut 8, together with the barrel and pinionassembly, to be traversed to the right until the movement of the pinionand the clutch disc 23 is arrested by the stop nut 12. Thereafter, thescrew-jack action of the screw shaft and control nut moves the thrustmember 13 against the driving clutch disc 23, compressing themesh-enforcing springs and forcing together the overrunning clutch teeth24. Since the longitudinal movement of the thrust member 18 is thusstopped, further movement of the control nut 8 forces the coupling discs14 against the preloaded springs 15 until suflicient torque is built upto cause the pinion 9 to rotate the engine gear 11, as shown in Fig. 2.

Preferably the pressure on the coupling discs 14 is limited in order topermit them to slip in case of overload. For this purpose, a thrust ring41 is interposed between the control nut and the thrust plate 18 inorder to limit the compression of the springs 15.

When the engine starts, the acceleration of the pinion 9 by the enginegear causes it to rotate faster than the starting motor, whereby thecontrol nut 8 moves back on the drive shaft 2 sutficiently to allow theoverrunning clutch teeth 24 to disengage, as shown in Fig. 3. Thiscondition continues until the rotation of the pinion is sufiicientlyrapid to withdraw the latch 34 by centrifugal force, after which theparts are traversed back to idle position, as shown in Fig. 1.

' In case, during the meshing movement, tooth abutment should occurbetween the pinion and engine gear, as shown in Fig. 4, themesh-enforcing springs 33 permit the barrel and control nut to moveforward while building up suflicient torque to index the pinion intoproper registry with the teeth of the engine gear. The springs 33 thenexpand and snap the pinion into initial mesh, thus avoiding milling theends of the teeth.

Although but one embodiment of the invention has been shown anddescribed in detail, it will be understood that other embodiments arepossible and that changes may be made in the precise form andarrangement of the parts without departing from the spirit of theinvention.

I'claim:

1. In an'engine starter drive, a drive shaft threaded for a portion ofits length, a control nut threaded thereon,

pinion in meshed position until it exceeds a predetermined rotativespeed.

3. An engine starter drive as set forth in claim 1 including furthermeans responsive to the screw-jack action of the drive shaft and controlnut for increasing the torque capacity of the friction coupling.

4. An engine starter drive as set forth in claim 1 in which saidoverrunning clutch connection comprises a driving clutch disc splined inthe barrel member, a driven pinion clutch member, means yieldinglyurging the clutch members into engagement, and an abutment on the driveshaft defining the meshed position of the pinion.

5. An engine starter drive as set forth in claim 4 including further apressure disc splined in the barrel member between the coupling discsand said clutch disc, a heavy compression spring between the couplingdiscs and the pressure disc, a lighter mesh enforcing spring between thepressure disc and the clutch disc, and means for limiting the expansionof the heavy compression spring.

6. An engine starter drive as set forth in claim 5 including furthermeans for limiting the compression of the coupling discs.

7. An engine starter drive as set forth in claim 6 including furthermeans for limiting the expansion of the mesh-enforcing spring, and meansincluding a light compression spring for 'yieldingly pressing the pinionclutch member against the driving clutch disc.

8. An engine starter drive as set forth in claim 2 including furthermeans on the drive shaft defining the idle position of the control nut,said drive shaft also having means cooperating with said latching meansfor yieldingly holding the pinion in idle position.

No references cited.

